1. Field
Embodiments of the present invention relate to a brake system having a drag reduction function and a method of controlling the same and, more particularly, to a brake system having a drag reduction function of effectively attenuating a drag phenomenon by controlling the position of a pressurizing piston in a pressurizing cylinder connected to a reserve tank through a motor to supply a fluid in a hydraulic line to the reserve tank such that negative pressure is created to force the piston in a caliper to be withdrawn, and a method of controlling the same.
2. Description of the Related Art
Generally, a vehicle is provided with a brake system to selectively decelerate or stop the vehicle when necessary during traveling. Such brake system usually performs the braking operation by converting the kinetic energy of the traveling vehicle into thermal energy using friction and dissipating the produced heat into the ambient air.
That is, such brake systems are generally classified into a drum brake system and a disc brake system. In the case of the disc brake system, braking force is obtained from frictional force generated when a caliper, which is driven by hydraulic pressure generated in a master cylinder according to manipulation of a brake pedal, applies pressure to brake pads on both sides of a brake disc.
The aforementioned brake systems prevent production of a lost travel section of a stroke by sensing that the driver presses the brake pedal and sending the pressure accumulated in an accumulator to wheel cylinders. With this method, however, if the hydraulic pressure by the driver's foot force becomes greater than the pressure accumulated in the accumulator, the accumulator may fail to send the accumulated pressure to the wheel, and rather the pressure produced by the driver's foot force may be accumulated, resulting in increase of the lost travel section of the stroke. If the pressure of the accumulator is significantly high, the pressure may be fully delivered when the driver depresses the brake pedal. This may significantly contribute to degradation of brake feel.
In addition, a conventional brake system as disclosed in Korean Patent Application Publication No. 2011-0125286 produces braking force through friction between the disc and the brake pads. This frictional force is produced by the brake pads pushed by the hydraulic pressure created through the driver's manipulation of the brake pedal. When braking is terminated, the frictional force is removed by separating the brake pads from the disc using the knock-back phenomenon occurring between the brake pads and resilience (roll-back phenomenon) of a piston seal of the disc caliper.
However, with this method, a drag phenomenon, which refers to incomplete separation of the brake pads from the disc, may frequently occur. In addition, service life of the brake pads may be reduced and output may be degraded due to unnecessary friction.
Accordingly, a brake system that is capable of completely separating the disc and the brake pads to reduce drag is needed.